When new, fuel injectors may exhibit some piece-to-piece variability. Over time, injector performance may degrade (e.g., injector becomes clogged) which may further increase piece-to-piece injector variability. As a result, the actual amount of fuel injected to each cylinder of an engine may not be the desired amount and the difference between the actual and desired amounts may vary between injectors. Such discrepancies can lead to reduced fuel economy, increased tailpipe emissions, and an overall decrease in engine efficiency. Further, engines operating with a plurality of different injection substances, such as different fuel mixtures, may have even more fuel injectors (e.g., twice as many) resulting in a greater possibility for degradation of engine performance due to injector degradation.
The inventor herein has recognized the above problems and has devised an approach to at least partially address them. Thus, a method for controlling fuel injection of a dual multi-substance injection engine which includes first and second fuel rails and first and second fuel pumps is disclosed. The method comprises, suspending pumping of a second substance into the second fuel rail and injecting a first substance to all but a single cylinder of the engine, and, while pumping is suspended in the second fuel rail, injecting the second substance into the single cylinder and correlating pressure decrease in the second fuel rail to injector operation.
By suspending pumping in the second fuel rail, an injector can be isolated and pressure drops in the fuel rail can be correlated to the operation of the injector. Further, injection of the first fuel can continue without interruption in all but one of the cylinders. In this manner, each fuel injector can be isolated and tested without significantly affecting engine operation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.